Method of setting diamonds or other abrasive



March 5, 1946. x A. J E ET AL 2,396,015

METHOD OF SETTING DIAMONDS QR dTHER ABRASiVE Filed March 13, 1942 v mally used it is METHOD or SETTING nmMoNns o'rnnn smmsrvr:

e Lidn, Stockholm, and Oscar Stockholm, Sweden,

Sundbyberg, near Malmborg,

assignors to Svenska Diamantbergborrnings Aktiebolaget, Stockholm, S

Sweden weden, a corporation of Application March 13, 1942, Serial No. 434,612 In Sweden March 21, 1941 2 Claims. (Cl. 51--309)v In making tools, it is well-known to set diamonds or other hard grains, such as mineral grains or grain's of various kinds of artificial materials, such as Carborundum (silicum carbide), in the tools and such settingis effected in accordance with several diiferent methods. Such tools are, for instance, diamond-set drill crowns for drilling in rock and stone, diamond-set saws for cutting stone, glass, ceramics etc., diamondset tools for turning and sharpening grinding wheels, and also grinding wheels, which often are made of Carborundum or other hard grains united by a binder.

When big grains, such as diamondspf a considerable size, are to be set in a toolf'the grain or crystal is often inserted into ahole drilled in the tool and then the material of the tool is pressed against the grain by means of punching. This method is convenient for securing big grains, but it is impractical or even impossible to carry out on small grains. In addition, for rendering such punching procedure possible the tool must be made of a material not too hard, and this reduces the resistance of the tool to wear and abrasion.

In many cases it is,however, suitable and very desirable to use small grains or crystals, because such small grains are stronger and sharper and, also less expensive, and have a better cutting action. To secure such small hard grains they were, for instance, laid in a metal powder and the latter was compressed at a high pressure, whereupon the bodies thus formed were sintered. In certain cases this renders relatively hard and solid bodies. However, the sintering method has vthe drawback that the metal powder with the hard grains therein usually must be compressed at extremely high pressures to cause the body thus shaped to sinter properly at the following heating procedure. There is consequently a risk of breaking or crushing weak grains. Another drawback is that in the sintering methods nor= possible to produce bodies of appreciable hardness and resistance to wear only by use of such powder mixtures which sinter at high temperatures. Consequently, if bodies with great hardness and resistance to wear were to be produced, it was necessary to use powder mixtures sintering at such high temperatures that there is a risk of damaging certain kinds of hard grains, such as diamonds, in which a graphitiza tion begins to take place at the high temper atures which are often necessary in this connection.

Another well-known method consists in cast= ing metal.

ing the hard grains in a comparatively low-melting and simultaneously relatively hard metal, for instance, certain copper and silver alloys. It is however, often difficult to cause the molten metal to enclose the hard grains completely. To overcome this drawback it was, for instance, proposed to silver the grains by precipitating a silver mirror on them, for instance, chemically. This certainly leads to an improvement in the result of the casting, but nevertheless it often turns out that thegrains are still not securely fastened. In a molten metal there are always gases which are liberated when the metal solidifies. When the silvered grains are introduced into the molten metal, the latter momentarily encloses all grains completely, but the thin silver foil around the grains soon melts or is alloyed with the molten metal, and then the gases contained in the molten metal have a tendency to be liberated and accumulate around the grains, because, due to the surface tension conditions, the molten metal often will not "wet the surfaces of the grains.

In cast tools or tool-bits made in accordance with the methods heretofore known the hard grains are rather loosely secured-and there is often a play between the This means that the grains soon fall out of the setting metal, when the tool is used.

This invention relates to a method of setting diamonds or other hard grains.

, The invention also relates to the products thus produced.

The chief purpose of this invention is to create tools, tool-bits and the like in which diamonds or other hard grains are set and which are very strong and resistant to shocks, wear and abrasion.

Another purpose of this invention is to manufacture such tools, tool-bits etc. without the necessity of subjecting the hard grains such as diamonds, to high temperature and high pressures.

Another purpose of this invention is to set diamonds and other hard grains in a setting material by means of a molten metal without any risk of air or gas bubbles being formed around the grains.

Other purposes of this invention will be evident. from the following specification and the claims.

One embodiment of this invention is illustrated in the annexed drawing, by way of example.

Fig. 1 is a vertical sectional view through a furnace for carrying out this invention.

Fig. 2 is a sectional view through in Fig. 1, on a larger scale.

grain and the surroundthe mold In accordance with the method of this in-:

vention the diamonds or. other hard grains are entirely packed in a powder having such small particles that the particles enter the unevennesses (minute recesses) in the surface of the hard grains and fill such recesses, whereupon without previous sintering of the powder a metal or an alloy having a lower melting point than that of the, powder is introduced (cast, poured) into the powder, the powder and the casting metal or alloy being selected in such manner that at the casting temperature the metal or alloy enters the powder and surrounds the particles of the powder and consequently also the hard grains and fills the interstices (pores) between the particles of the powder. It turns out that thus the hard grains are permanently set and that the powder and the casting metal or alloy form a hard and resistant setting so that the tool will have a high resistance to abrasion and wear. No air or gas bubbles are formed in the powder or between it and the hard grains and consequently the. latter have no tendency to get loose.

The size of the powder particles should preferably be so small that the powder may be packed well and then will completely enclose the hard grains and fill the minute recesses in the surface of said grains. The upper limit of the size of these particles can be found by experiments and in practice there seems to be no lower limit.

A suitable size of the powder particles is, for

instance, 0.002 mm.

Preferably, the powder is packed around the hard grains. For instance, the hard grains may be mixed into the powder which is then packed. If the hard grains have a high resistance to compressive strains, it is in certain cases preferred to compress the powder under high pressure, instead of only packing it. The packed powder together with the hard grains therein is brought into contact with a suitable metal or metal alloy. For this purpose, the packed powder together with the metal may be heated to such high temperature that the metal melts and enters the packed powder and encloses the powder particles. It is, however, also possible to pour the molten metal on the powder or to dip the powder (mouldin of powder) into the molten metal or to permit the powder to suck in the molten metal in any other way. Whatever method is used for this purpose, both the powder particles and the hard grains will be well enclosed by the molten metal which fills all recesses, interstices and pores. It

turns out that in the practice no gas bubbles are originated round the hard grains or in the powder proper. This is also true when the powder is only loosely packed, that is: packed without the use of substantial pressure. Care should be taken that enough casting metal (molten metal) is used so that the packed powder will be sufficiently saturated. It is often preferable or even neces-, sary to use a fiuxas in soldering-to facilitate the penetration of the molten metal or alloy into the packed powder. As a flux, borax may be used.

It is also possible to place pieces of the metal or alloy together with the flux, if any, on the powder or moulding of powder, and then the metal and the powder are heated in a furnace having a reducing atmosphere, such as a hydrogen atmosphere, until the metal melts and becomes sufficiently fluid to penetrate into the powder. In some cases it is advantageous to effect also the subsequent cooling procedure in a reducing atmosphere.

If the casting metal is hard solder or copper, the powder may, for instance, consist of cobalt, nickel, iron or tungsten carbide or a mixture thereof, according to the desired qualities of the finished setting material around the hard grains.

The annexed drawing illustrates our invention. Fig. 1 shows a furnace I which is heatedelectrically through the conductors 2. To the interior of said furnace hydrogen may be supplied through the tube 3 to create a reducing atmosphere within the furnace. Into the furnace a mold 4 is inserted.

This mold and its contents are illustrated in Fig. 2. The mold l proper may be made of graphite or clay. Up to a certain level, this mold 4 is filled with diamonds 5 or other hard grains, packed in or simply mixed with a powder 6 of iron. The size of grain of said metal powder 6 is small compared with that of the diamonds 5, so that the metal powder particles enter and substantially fill the unevennesses of 'the diamonds. Upon this mixture of diamonds and iron powder a layer 1 of a suitable flux is laid, and upon said layer a piece 8 of copper or hard solder.

In the furnace, the mold is heated to such temperature that the solder 8 melts and penetrates into the powder, so that after cooling the diamonds are securely fixed in the homogenous compound of solder and iron powder.

The result is illustrated in Figs. 3 and 4. Fig. 3 shows a diamond 5 surrounded by the metal compound. Fig. 4 shows a very magnified section through an unevenness in the diamond and the adjacent metal compound. Said compound consists of the iron powder particles 6 which are on all sides surrounded by and tightly enclosed in the solder or copper 9. The metallic mass 6, 9 is not porous but thoroughly solid. It grips the diamond very hard and keeps it securely fixed, even if subjected to high stresses and strains.

The qualities of the setting material dependamong other factors-upon the nature of the powder and the casting metal used, but also the degree of packing of the powder before the casting has a considerable influence. Thus, for instance, the hardness is increased in the same degree as the packing of the powder is increased provided that a powder is used which is harder than the casting metal. The harder the material of the powder is, the harder also the setting material becomes. The harder the casting metal is, the harder also the setting material will be.

The proportions of powder and casting metal in the finished setting material also have an infiuence upon the hardness of the latter. If a very hard and resistant setting material is to be produced, which is advantageous for most tools, fine-grained, packed tungsten carbide powder may be used which is combined with copper as casting metal.

By selecting various powders and difierent kinds of casting metal and by varying the degree of packing or compression, it is possible to vary. within wide limits, the hardness of the setting material for the hard grains.

In many cases, it is necessary to adjust the hardness and particularly the resistance of the setting material to wear, to a precisely pre-de- 1 limits.

7 may be set securely,

be given, diilerent qualities strength, resistance to wear etc.,

' whichis not wetted by .wetted by said material to wear by is not the casting metal, to the casting metallic material. has an influence upon the hardness of the finished setting materials This hardness may consequently is possibleito control bedded, said latter powder being wettable by the casting metal; Silicium carbide powder is not wetted by the casting metal and may be used for this purpose. The greater the quantity of such admixed powder is, the ance of the setting material to abrasion. This renders it possible to adjust the resistance to abrasion to the desired value within narrow no special precautions are taken. Forinstance,

the powder may be caused to enclose the hard grains very efilciently, by first moistening the hard grains with a liquid w ch evaporates when heated to the casting temperature. The moist grains are then admixed to the powder, in which they are to be packed, so that the powder adheres to the lower is the resist a casting into said powder mixture a metallic matealso be varied by varying the size of said particles of the second powder. The casting metallic material should fill at least %of the total volume of the article produced.

Goodresults are attained when said casting metallic material fills or even 50% or more of the total volume.v

what we claim is:

1. A method of setting hard grains in a setting material, comprising, mixing in a predetermined proportion two powders having such small particles that they are able to enter and substantially 'fill the unevennesses of the hard grains; embedding the hard grains in said powder mixture; and

1 rial having a lower melting point than the lowest the hard grains are sur- 7 meltingpoint of any of said powders and also having a definite ability of wetting one-of said powders substantially in the absence of-oxidizing mate ter, but being unable to wet the other powder; the

moist surfaces of the grains and forms a coating onthem. "The thickness of such coatingdepends upon the qualities of the liquid used and to some extent also upon those of the powder.

In accordance with this invention hard grains strongly and'at low costs in'a material which in accordance with the want may withinwide limits, for instance, in respect of hardness, tenacity,

aswanted without the necessity of subjecting the grainsto high pressures or very high temperature. 'Consequently, the hard grains are set in an undamaged state in the setting material.

The products produced in'accordance with this invention, such :as shaped bodies, in which the hard grains are set, may either directly be used as tools for different purposes or insuitable manner,

' for instance, by soldering, be secured in or to holders of suitable material and form to be used as tools'together with them. Thus, for instance, diamond drilling crowns, diamond saws, grinding wheels, diamond tools for sharpening grinding wheels, high-speed turning tools etc. may be produced in accordance with this invention. 7 The size of the particles of the second powder the castin metallic material and is admixedto the first powder which is casting procedure being effected substantially in the absence of oxidizing matter and without any previous sintering of the powder mixture, which contains said two powders in such proportion as to render a suitable, predetermined resistance to wear in the finished setting material of powder mixture and solidified metallic material; said powder and said metallic casting material, after the latter has solidified, forming a strong holding material for the hard grains and being so resistant to wear and abrasion that they are not worn off prematurely in working operations but safely hold the hardgrains, until the latter have become blunt and worn out in use.

2. A method of setting hard grains in a setting material. comprising embedding the hard grains in a tungsten carbide powder with such small particles that they are able to enter and substantially fill the unevennesses in the hard grains; and casting copper'intothe tungsten carbide powder,

without previously sintering the powder, and substantially in the absence of oxidizing matter at,

that the copper enters the tungsten carbide 'powder and envelops the tungsten carbide powder particles, thus also enveloping the hard grains and substantiallyfiliing the unevennesses thereof and sten carbide powder;

the interstices between the particles of the tunglic casting material, after the latter has solidified. forming a strong holding material for the hard grains and being so resistant to wearand abrasion that they are not worn off prematurely in work'- ing operations but safely hold the hard grains, un-

til the latter have become blunt and worn out in use.

OSCAR MALMBORG.

said powder and said metal--- 

